1. Chapter 6 Behavior of Gases

2. When substances are in the Gas Phase, there is a unique result. All substances while in the gas phase behave the same. We can look at a few of these. Molecules are relatively far apart and therefore they don’t attract each other. Molecules are in constant motion, moving faster at higher temperatures. Gases exert pressure when molecules hit the walls of their container. Gases fill their containers because they don’t attract each other. Gases obey the Gas Laws. Two of these are:

3.  Boyle’s Law - 1662 - named after Robert Boyle (the same person who gave us the modern definition of an element)  Charles’ Law – French Physicist – Jacques Charles - 1787

4. © 2010 Pearson Prentice Hall, Inc. 6/4 Boyle’s law: At constant temperature, the volume of a gas is inversely proportional to its pressure.

5. © 2010 Pearson Prentice Hall, Inc. 6/5 Charles’s law: At constant pressure, the volume of a gas is directly proportional to its absolute temperature.

6. Absolute Temperature is designated kelvins or K. Named after William Thomson – Lord Kelvin - 1848 Mathematically: K = °C + 273 When doing gas law calculations, we need to use a different temperature scale than Celsius or Fahrenheit. It is called the Absolute Temperature scale or Kelvin Temperature scale. 0 on the Absolute scale is the lowest possible temperature.

7. © 2010 Pearson Prentice Hall, Inc. 6/7 Charles’s Law Balloon At liquid nitrogen temp: -196°C or 77 K Same balloon at Room Temp